1. Field of the Invention
This invention relates to integrated circuit products. More particularly, the invention relates to a method or process for determining a load line based variable voltage input for an integrated circuit product.
2. Description of Related Art
Integrated Circuit (IC) products (e.g. processors, central processing units (CPU), chipsets, graphic chips, etc.) generally require a voltage input (often termed a voltage core input (Vcc)) from a voltage regulator to operate. This voltage input (Vcc) is complimented by a current input (Icc), which results from the voltage Vcc and the IC product""s effective impedance. This current Icc input can vary across IC product performance offerings where IC products of the same family but with higher internal clock frequencies typically draw more current Icc for a given voltage input (Vcc). In today""s cost effective IC product designs, typically, as the current draw Icc increases, the IC product""s input voltage Vcc tends to decrease, due to the voltage droop of path parasitics and regulator and capacitor resistances. Furthermore, in order to maintain product performance and yield, IC products continuously require a minimum voltage closer to the nominal input voltage Vcc requirement set for the IC product (e.g. a Voltage Identifier (VID) setting for CPU""s). This becomes even more pronounced as voltage input (Vcc) levels decrease due to silicon process improvements and size reductions, as keeping the same input voltage range would require a larger percentage of the operational voltage level as voltage decreases. Excessive voltage droop can result in an unstable IC product due to speed path issues. However, directly compensating for tighter voltage regulation ranges results in a significant cost increase in the voltage regulator and can impact the viability of the IC product.
Unfortunately, current design practice is to specify a set non-varying minimum and maximum input voltage Vcc requirement for all Icc load in IC product specifications, which does not take into account that in today""s IC products, as current draw Icc increases, the IC product""s input voltage Vcc tends to decrease. Accordingly, absolute maximum and minimum voltage specifications apply to any current draw Icc which allows significantly different voltage regulator performance from manufacturer to manufacturer and from design to design. Moreover, voltage and current are not correlated and all IC products need to be manufactured and tested based upon the single worst-case maximum and minimum voltage specifications.